Understanding NRT- Reading 1 of 2- Radiogaphic Testing A

Understandings 

NRT - Reading 1 

Radiographic Testing 

2 nd Pre-exam self study 

note for Neutron 

Radiographic Testing 

2 nd April 2016 

Charlie Chong/ Fion Zhang

NDT for Upstream 



Charlie Chong/ Fion Zhang 

Fion Zhang at Xitang 

1 st April 2016


SME- Subject Matter Expert 

我们的大学 , 其实应该聘请这些能干的退休教授 . 

或许在职的砖头怕被排斥 . 

http://cn.bing.com/videos/search?q=Walter+Lewin&FORM=HDRSC3 

https://www.youtube.com/channel/UCiEHVhv0SBMpP75JbzJShqw

NR - Neutron Radiographic Testing 

Length: 4 hours Questions: 135 

1. Principles/ Theory 

• Nature of penetrating radiation 

• Interaction between penetrating radiation and matter 

• Neutron radiography imaging 

• Radiometry 

2. Equipment/Materials 

• Sources of neutrons 

• Radiation detectors 

• Nonimaging devices 


3. Techniques/Calibrations 

• Blocking and filtering 

• Multifilm technique 

• Enlargement and projection 

• Stereoradiography 

• Triangulation methods 

• Autoradiography 

• Flash Radiography 

• In-motion radiography 

• Fluoroscopy 

• Electron emission radiography 

• Microradiography 

• Laminography (tomography) 

• Control of diffraction effects 

• Panoramic exposures 

•Gaging 

• Real time imaging 

• Image analysis techniques 


4. Interpretation/Evaluation 

• Image-object relationships 

• Material considerations 

• Codes, standards, and specifications 

5. Procedures 

• Imaging considerations 

• Film processing 

• Viewing of radiographs 

• Judging radiographic quality 

6. Safety and Health 

• Exposure hazards 

• Methods of controlling radiation exposure 

• Operation and emergency procedures 


http://www.yumpu.com/zh/browse/user/charliechong 

http://issuu.com/charlieccchong 



http://greekhouseoffonts.com/

The Magical Book of Tank Inspection ICP 



闭门练功 


Industrial Radiography 


Khanacademy 


https://www.khanacademy.org/science/chemistry/nuclear-chemistry/radioactive-decay/v/types-of-decay

Chapter 1: History of 

Radiography 

X-rays were discovered in 1895 by Wilhelm 

Conrad Roentgen (1845-1923) who was a 

Professor at Wuerzburg University in Germany. 

Working with a cathode-ray tube in his laboratory, 

Roentgen observed a fluorescent glow of crystals 

on a table near his tube. The tube that Roentgen 

was working with consisted of a glass envelope 

(bulb) with positive and negative electrodes 

encapsulated in it. The air in the tube was 

evacuated, and when a high voltage was applied, 

the tube produced a fluorescent glow. Roentgen 

shielded the tube with heavy black paper, and 

discovered a green colored fluorescent light 

generated by a material located a few feet away 

from the tube. 


He concluded that a new type of ray was being emitted from the tube. This 

ray was capable of passing through the heavy paper covering and exciting 

the phosphorescent materials in the room. He found the new ray could pass 

through most substances casting shadows of solid objects. Roentgen also 

discovered that the ray could pass through the tissue of humans, but not 

bones and metal objects. One of Roentgen's first experiments late in 1895 

was a film of the hand of his wife, Bertha. It is interesting that the first use of 

X-rays were for an industrial (not medical) application as Roentgen produced 

a radiograph of a set of weights in a box to show his colleagues. 


Wuerzburg University 


Roentgen's discovery was a scientific bombshell, 

and was received with extraordinary interest by 

both scientist and laymen. Scientists everywhere 

could duplicate his experiment because the 

cathode tube was very well known during this 

period. Many scientists dropped other lines of 

research to pursue the mysterious rays. 

Newspapers and magazines of the day provided 

the public with numerous stories, some true, 

others fanciful, about the properties of the newly 

discovered rays. 


Taking an X-ray image with early Crookes tube 

apparatus, late 1800s. The Crookes tube is visible 

in center. The standing man is viewing his hand 

with a fluoroscope screen. No precautions against 

radiation exposure are taken; its hazards were not 

known at the time. 



Public fancy was caught by this invisible ray with the ability to pass through 

solid matter, and, in conjunction with a photographic plate, provide a 

picture of bones and interior body parts. Scientific fancy was captured by 

demonstration of a wavelength shorter than light. This generated new 

possibilities in physics, and for investigating the structure of matter. Much 

enthusiasm was generated about potential applications of rays as an aid in 

medicine and surgery. Within a month after the announcement of the 

discovery, several medical radiographs had been made in Europe and the 

United States which were used by surgeons to guide them in their work. In 

June 1896, only 6 months after Roentgen announced his discovery, X-rays 

were being used by battlefield physicians to locate bullets in wounded 

soldiers. 


Battlefield 


http://www.iimeffwd.marines.mil/Photos.aspx?igphoto=2000023630

Battlefield 



Battlefield 



Prior to 1912, X-rays were used little outside the realms of medicine, and 

dentistry, though some X-ray pictures of metals were produced. The reason 

that X-rays were not used in industrial application before this date was 

because the X-ray tubes (the source of the X-rays) broke down under the 

voltages required to produce rays of satisfactory penetrating power for 

industrial purpose. However, that changed in 1913 when the high vacuum X- 

ray tubes designed by Coolidge became available. The high vacuum tubes 

were an intense and reliable X-ray sources, operating at energies up to 

100,000 volts. (0.1Mv) 

In 1922, industrial radiography took another step forward with the advent of 

the 200,000-volt X-ray tube that allowed radiographs of thick steel parts to be 

produced in a reasonable amount of time. In 1931, General Electric Company 

developed 1,000,000 volt X-ray generators, providing an effective tool for 

industrial radiography. That same year, the American Society of Mechanical 

Engineers (ASME) permitted X-ray approval of fusion welded pressure 

vessels that further opened the door to industrial acceptance and use. 


A Second Source of Radiation 

Shortly after the discovery of X-rays, another form of penetrating rays was 

discovered. In 1896, French scientist Henri Becquerel discovered natural 

radioactivity. Many scientists of the period were working with cathode rays, 

and other scientists were gathering evidence on the theory that the atom 

could be subdivided. Some of the new research showed that certain types of 

atoms disintegrate by themselves. It was Henri Becquerel who discovered 

this phenomenon while investigating the properties of fluorescent minerals. 

Becquerel was researching the principles of fluorescence, certain minerals 

glow (fluoresce) when exposed to sunlight. He utilized photographic plates to 

record this fluorescence. 


One of the minerals Becquerel worked with was a uranium compound. On a 

day when it was too cloudy to expose his samples to direct sunlight, 

Becquerel stored some of the compound in a drawer with his photographic 

plates. Later when he developed these plates, he discovered that they were 

fogged (exhibited exposure to light.) Becquerel questioned what would have 

caused this fogging? He knew he had wrapped the plates tightly before using 

them, so the fogging was not due to stray light. In addition, he noticed that 

only the plates that were in the drawer with the uranium compound were 

fogged. Becquerel concluded that the uranium compound gave off a type of 

radiation that could penetrate heavy paper and expose photographic film. 

Becquerel continued to test samples of uranium compounds and determined 

that the source of radiation was the element uranium. Bacquerel's discovery 

was, unlike that of the X-rays, virtually unnoticed by laymen and scientists 

alike. Only a relatively few scientists were interested in Becquerel's findings. It 

was not until the discovery of radium by the Curies two years later that 

interest in radioactivity became wide spread. 


Becquerel 


While working in France at the time of 

Becquerel's discovery, Polish scientist 

Marie Curie became very interested in 

his work. She suspected that a 

uranium ore known as pitchblende 

contained other radioactive elements. 

Marie and her husband, a French 

scientist, Pierre Curie started looking 

for these other elements. In 1898, the 

Curies discovered another radioactive 

element in pitchblende, they named it 

'polonium' in honor of Marie Curie's 

native homeland. Later that year, the 

Curie's discovered another radioactive 

element which they named 'radium', or 

shining element. Both polonium and 

radium were more radioactive than 

uranium. Since these discoveries, 

many other radioactive elements have 

been discovered or produced. 


Radium became the initial industrial gamma ray source. The material allowed 

radiographing castings up to 10 to 12 inches thick. During World War II, 

industrial radiography grew tremendously as part of the Navy's shipbuilding 

program. In 1946, manmade gamma ray sources such as cobalt and iridium 

became available. These new sources were far stronger than radium and 

were much less expensive. The manmade sources rapidly replaced radium, 

and use of gamma rays grew quickly in industrial radiography. 



Health Concerns 

The science of radiation protection, or "health physics" as it is more properly 

called, grew out of the parallel discoveries of X-rays and radioactivity in the 

closing years of the 19th century. Experimenters, physicians, laymen, and 

physicists alike set up X-ray generating apparatus and proceeded about their 

labors with a lack of concern regarding potential dangers. Such a lack of 

concern is quite understandable, for there was nothing in previous experience 

to suggest that X-rays would in any way be hazardous. Indeed, the opposite 

was the case, for who would suspect that a ray similar to light but unseen, 

unfelt, or otherwise undetectable by the senses would be damaging to a 

person? More likely, or so it seemed to some, X-rays could be beneficial for 

the body. 

Inevitably, the widespread and unrestrained use of X-rays led to serious 

injuries. Often injuries were not attributed to X-ray exposure, in part because 

of the slow onset of symptoms, and because there was simply no reason to 

suspect X-rays as the cause. Some early experimenters did tie X-ray 

exposure and skin burns together. The first warning of possible adverse 

effects of X-rays came from Thomas Edison, William J. Morton, and Nikila 

Tesla who each reported eye irritations from experimentation with X-rays and 

fluorescent substances. 


Today, it can be said that radiation ranks among the most thoroughly 

investigated causes of disease. Although much still remains to be learned, 

more is known about the mechanisms of radiation damage on the molecular, 

cellular, and organ system than is known for most other health stressing 

agents. Indeed, it is precisely this vast accumulation of quantitative doseresponse 

data that enables health physicists to specify radiation levels so that 

medical, scientific, and industrial uses of radiation may continue at levels of 

risk no greater than, and frequently less than, the levels of risk associated 

with any other technology. 

X-rays and Gamma rays are electromagnetic radiation of exactly the same 

nature as light, but of much shorter wavelength. Wavelength of visible light is 

of the order of 6000 angstroms while the wavelength of x-rays is in the range 

of one angstrom and that of gamma rays is 0.0001 angstrom. This very short 

wavelength is what gives x-rays and gamma rays their power to penetrate 

materials that light cannot. 


These electromagnetic waves are of a high energy level and can break 

chemical bonds in materials they penetrate. If the irradiated matter is living 

tissue the breaking of chemical bond may result in altered structure or a 

change in the function of cells. 

Early exposures to radiation resulted in the loss of limbs and even lives. Men 

and women researchers collected and documented information on the 

interaction of radiation and the human body. This early information helped 

science understand how electromagnetic radiation interacts with living tissue. 

Unfortunately, much of this information was collected at great personal 

expense. 





http://v.youku.com/v_show/id_XMTY1MzAwMTQw.html
















Present State of Radiography 

In many ways radiography has changed little from the early days of its use. 

We still capture a shadow image on film using similar procedures and 

processes technicians were using in the late 1800's. Today, however, we are 

able to generate images of higher quality, and greater sensitivity through the 

use of higher quality films with a larger variety of film grain sizes. Film 

processing has evolved to an automated state producing more consistent film 

quality by removing manual processing variables. Electronics and computers 

allow technicians to now capture images digitally. The use of "filmless 

radiography" provides a means of capturing an image, digitally enhancing, 

sending the image anywhere in the world, and archiving an image that will not 

deteriorate with time. Technological advances have provided industry with 

smaller, lighter, and very portable equipment that produce high quality X-rays. 

The use of linear accelerator provide a means of generating extremely short 

wavelength, highly penetrating radiation, a concept dreamed of only a few 

short years ago. While the process has changed little, technology has 

evolved allowing radiography to be widely used in numerous areas of 

inspection. 


Filmless Radiography 


http://www.ari.com.au/digital-radiography.html

Filmless 

Radiography 







Radiography has seen expanded usage in industry to inspect not only welds 

and castings, but to radiographically inspect items such as airbags and caned 

food products. Radiography has found use in metallurgical material 

identification and security systems at airports and other facilities. 

Gamma ray inspection has also changed considerably since the Curies' 

discovery of radium. Man-made isotopes of today are far stronger and offer 

the technician a wide range of energy levels and half-lives. The technician 

can select Co-60 which will effectively penetrate very thick materials, or select 

a lower energy isotope, such as Thulium, Tm-170, which can be used to 

inspect plastics and very thin or low density materials. Today gamma rays 

find wide application in industries such as petrochemical, casting, welding, 

and aerospace. 

Keywords: 

Linac 

Filmless radiography 

Film grain sizes 


https://en.wikipedia.org/wiki/Isotopes_of_thulium


https://en.wikipedia.org/wiki/Isotopes_of_thulium

Nature of Penetrating Radiation 

X-rays and gamma rays are part of the electromagnetic spectrum. They are 

waveforms as are light rays, microwaves, and radio wave, but x-rays and 

gamma rays cannot been seen, felt, or heard. They possess no charge and 

no mass and, therefore, are not influenced by electrical and magnetic fields 

and will always travel in straight lines. They can be characterized by 

frequency, wavelength, and velocity. However, they act somewhat like a 

particle at times in that they occur as small "packets" of energy and are 

referred to as "photon." 




X-rays and gamma rays differ only in their source of origin. X-rays are 

produced by an x-ray generator, which will be discussed a little latter. Gamma 

radiation, which will be the focus of discussion here, is the product of 

radioactive atoms. Depending upon the ratio of neutrons to protons within its 

nucleus, an isotope of a particular element may be stable or unstable. Over 

time the nuclei of unstable isotopes spontaneously disintegrate, or transform, 

in a process known as radioactive decay. Various types of ionizing radiation 

may be emitted from the nucleus and/or its surrounding electrons. Nuclides 

which undergo radioactive decay are called radionuclides. Any material which 

contains measurable amounts of one or more radionuclides is a radioactive 

material. 

The degree of radioactivity or radiation producing potential of a given amount 

of radioactive material is measured in Curies (Ci). The curie which was 

originally defined as that amount of any radioactive material which 

disintegrates at the same rate as one gram of pure radium. The curie has 

since been defined more precisely as a quantity of radioactive material in 

which 3.7 x 10 10 atoms disintegrate per second. The International System (SI) 

unit for activity is the Becquerel (Bq), which is that quantity of radioactive 

material in which one atom is transformed per second. 


Keywords: 

The curie - 3.7 x 1010 atoms disintegrate per second. 

The Becquerel (Bq) - one atom is transformed per second. 


Beta Decay 

During beat decay, the parent nuclei emitted beta rays which made up of a 

beta particle. Beta particle is a fast moving electron or positron which 

depends on the type on beta decay involved. 

0 n1 → → 1 p1 + -1 

e 1 + Ï… 


http://chemistry.tutorvista.com/nuclear-chemistry/alpha-decay.html

Alpha Decay Definition 

toms with more number of neutrons and protons are highly unstable and get 

stabilized by emission alpha particles. The emission of alpha particles from 

parent nuclei to form new daughter nuclei is called as alpha decay. 

a Xb → → a-2 Yb-4 + 2 

He 4 


The radioactivity of a given amount of radioactive material does not depend 

upon the mass of material present. For example, two one-curie sources of 

Cs-137 might have very different masses depending upon the relative 

proportion of non-radioactive atoms present in each source. Radioactivity is 

expressed as the number of curies or becquerels per unit mass or volume. 

Each radionuclide decays at its own unique rate which cannot be altered by 

any chemical or physical process. 

A useful measure of this rate is the half-life of the radionuclide. Half-life is 

defined as the time required for the activity of any particular radionuclide to 

decrease to one-half of its initial value, or one-half of the atoms to change to 

daughter atoms reverting to a stable state material. Half-lives of radionuclides 

range from microseconds to billions of years. Half-life of two widely used 

industrial isotopes are 75 days for Iridium-192, and 5.3 years for Cobalt-60. 

More exacting calculations can be made for the half-life of these materials, 

however, these times are commonly used by technicians. 


Keywords: 

Half-life of two widely used industrial isotopes are for: 

T ½ Iridium-192- 75 days 

T ½ Cobalt-60- 5.3 years 


https://en.wikipedia.org/wiki/Cobalt-60

Cobalt-60, 60Co, is a synthetic radioactive isotope of cobalt with a half-life of 

5.2714 years. It is produced artificially in nuclear reactors. Deliberate 

industrial production depends on neutron activation of bulk samples of the 

monoisotopic and mononuclidic cobalt isotope 59Co.Measurable quantities 

are also produced as a by-product of typical nuclear power plant operation 

and may be detected externally when leaks occur. In the latter case (in the 

absence of added cobalt) the incidentally produced 60Co is largely the result 

of multiple stages of neutron activation of iron isotopes in the reactor's steel 

structures via the creation of 59 60Co precursor. The simplest case of the latter 

would result from the activation of 58 26 Fe. 60 27Co decays by beta decay to the 

stable isotope nickel-60 (60Ni). The activated nickel nucleus emits two 

gamma rays with energies of 1.17 and 1.33 MeV, hence the overall nuclear 

equation of the reaction is 

59 

27 Co + n → 60 27 Co → 60 28 Ni + e− + ν e 

+ gamma rays 

58 

26 Fe + n → 59 26 Fe → 59 27Co + e− + νe + gamma rays 



Half Life Equation: 


Types Ionizing Radiation 

When an atom undergoes radioactive decay, it emits one or more forms of 

ionizing radiation, defined as radiation with sufficient energy to ionize the 

atoms with which it interacts. Ionizing radiation can consist of high speed 

subatomic particles ejected from the nucleus or electromagnetic radiation 

(gamma-rays) emitted by either the nucleus or orbital electrons. 

Alpha Particles α 2+ , He 2+ 

Certain radionuclides of high atomic mass (Ra226, U238, Pu239) decay by 

the emission of alpha particles. These alpha particles are tightly bound units 

of two neutrons and two protons each ( 4 2 He2+ nucleus) and have a positive 

charge. Emission of an alpha particle from the nucleus results in a decrease 

of two units of atomic number (Z) and four units of mass number (A). Alpha 

particles are emitted with discrete energies characteristic of the particular 

transformation from which they originate. All alpha particles from a particular 

radionuclide transformation will have identical energies. 


Alpha Particle 


https://en.wikipedia.org/wiki/Alpha_particle

Alpha particles consist of two protons and two neutrons bound together into a 

particle identical to a helium nucleus. They are generally produced in the 

process of alpha decay, but may also be produced in other ways. Alpha 

particles are named after the first letter in the Greek alphabet, α. The symbol 

for the alpha particle is α or α 2+ . Because they are identical to helium nuclei, 

they are also sometimes written as He 2+ or 4 2 He2+ indicating a helium ion 

with a +2 charge (missing its two electrons- why do these electron go? Kinetic 

energy? ). If the ion gains electrons from its environment, the alpha particle 

can be written as a normal (electrically neutral) helium atom 4 2He (g) . 


Alpha particles, like helium nuclei, have a net spin of zero. Due to the 

mechanism of their production in standard alpha radioactive decay, alpha 

particles generally have a kinetic energy of about 5 MeV, and a velocity in the 

vicinity of 5% the speed of light. (See discussion below for the limits of these 

figures in alpha decay.) They are a highly ionizing form of particle radiation, 

and (when resulting from radioactive alpha decay) have low penetration depth. 

They are able to be stopped by a few centimeters of air, or by the skin. 

However, so-called long range alpha particles from ternary fission are three 

times as energetic, and penetrate three times as far. As noted, the helium 

nuclei that form 10–12% of cosmic rays are also usually of much higher 

energy than those produced by nuclear decay processes, and are thus 

capable of being highly penetrating and able to traverse the human body and 

also many meters of dense solid shielding, depending on their energy. To a 

lesser extent, this is also true of very high-energy helium nuclei produced by 

particle accelerators. 


When alpha particle emitting isotopes are ingested, they are far more 

dangerous than their half-life or decay rate would suggest, due to the high 

relative biological effectiveness of alpha radiation to cause biological damage, 

after alpha-emitting radioisotopes enter living cells. Ingested alpha emitter 

radioisotopes (such as transuranics or actinides) are an average of about 20 

times more dangerous, and in some experiments up to 1000 times more 

dangerous, than an equivalent activity of beta emitting or gamma emitting 

radioisotopes. 

In computer technology, dynamic random access memory (DRAM) "soft 

errors" were linked to alpha particles in 1978 in Intel's DRAM chips. The 

discovery led to strict control of radioactive elements in the packaging of 

semiconductor materials, and the problem is largely considered to be solved. 


Anti-alpha particle 

In 2011, members of the international STAR collaboration using the 

Relativistic Heavy Ion Collider at the U.S. Department of Energy's 

Brookhaven National Laboratory detected the antimatter partner of the helium 

nucleus, also known as the anti-alpha.[13] The experiment used gold ions 

moving at nearly the speed of light and colliding head on to produce the 

antiparticle 


http://web2.uwindsor.ca/courses/physics/high_schools/2013/Antimatter/history.html

Anti-alpha particle 


http://www.nbcnews.com/science/space/stephen-hawking-gets-star-treatment-theory-everything-n238441


A Brief History of 

Antimatter 

Antimatter has been a 

topic of great interest 

for physics enthusiasts 

for the past 100 years. 

As a relatively new 

topic there have been 

many recent advances 

in the theory and 

technology that has 

allowed us to observe 

this phenomenon. The 

timeline below outlines 

some of key people and 

ideas behind our recent 

understanding of 

antimatter.

Beta Particles 

A nucleus with an unstable ratio of neutrons to protons may decay through 

the emission of a high speed electron called a beta particle. This results in a 

net change of one unit of atomic number (Z). Beta particles have a negative 

charge and the beta particles emitted by a specific radionuclide will range in 

energy from near zero up to a maximum value, which is characteristic of the 

particular transformation. (A number remains the same) 

Gamma-rays 

A nucleus which is in an excited state may emit one or more photons (packets 

of electromagnetic radiation) of discrete 分立的 energies. The emission of 

gamma rays does not alter the number of protons or neutrons in the nucleus 

but instead has the effect of moving the nucleus from a higher to a lower 

energy state (unstable to stable). Gamma ray emission frequently follows 

beta decay, alpha decay, and other nuclear decay processes. 


X-rays are also part of the electromagnetic spectrum and are distinguished 

from gamma rays only by their source (orbital electrons rather than the 

nucleus). X-rays are emitted with discrete energies by electrons as they shift 

orbits following certain types of nuclear decay processes. Internal conversion 

occurs in a isotope when the energy is transferred to an atomic origin electron 

that is then ejected with kinetic energy equal to the expected gamma ray, but 

minus the electron's binding energy. The vacancy in the atomic structure is 

filled by an external electron, resulting in the production of x-rays. Thulium- 

170 is a good example of this type of disintegration. When Thulium-170 

looses its energy it will exhibit a 60 % probability of interaction with an orbital 

electron thus producing x-radiation. 


Characteristic X-rays are emitted when outer-shell electrons fill a vacancy in 

the inner shell of an atom, releasing X-rays in a pattern that is "characteristic" 

to each element. Characteristic X-rays were discovered by Charles Glover 

Barkla in 1909, who later won the Nobel Prize in Physics for his discovery in 

1917. 


https://en.wikipedia.org/wiki/Characteristic_X-ray

Characteristic X-rays are produced when an element is bombarded with highenergy 

particles, which can be photons, electrons or ions (such as protons). 

When the incident particle strikes a bound electron (the target electron) in an 

atom, the target electron is ejected from the inner shell of the atom. After the 

electron has been ejected, the atom is left with a vacant energy level, also 

known as a core hole. Outer-shell electrons then fall into the inner shell, 

emitting quantized photons with an energy level equivalent to the energy 

difference between the higher and lower states. Each element has a unique 

set of energy levels, and thus the transition from higher to lower energy levels 

produces X-rays with frequencies that are characteristic to each element. 

When an electron falls from the L shell to the K shell, the X-ray emitted is 

called a K-alpha X-ray. Similarly, when an electron falls from the M shell to 

the K shell, the X-ray emitted is called a K-beta X-ray.[3] Sometimes, however, 

instead of releasing the energy in the form of an X-ray, the energy can be 

transferred to another electron, which is then ejected from the atom. This is 

known as the Auger effect, and the second ejected electron is known as an 

Auger electron. 


https://en.wikipedia.org/wiki/Characteristic_X-ray

In an X-ray tube, electrons are accelerated in a vacuum by an electric field 

and shot into a piece of metal called the "target". X-rays are emitted as the 

electrons slow down (decelerate) in the metal. The output spectrum consists 

of a continuous spectrum of X-rays, with additional sharp peaks at certain 

energies (see graph on right). The continuous spectrum is due to 

bremsstrahlung, while the sharp peaks are characteristic X-rays associated 

with the atoms in the target. For this reason, bremsstrahlung in this context is 

also called continuous X-rays. 

The spectrum has a sharp cutoff at low wavelength, which is due to the 

limited energy of the incoming electrons. For example, if an electron in the 

tube is accelerated through 60 kV, then it will acquire a kinetic energy of 60 

keV, and when it strikes the target it can create X-rays with energy of at most 

60 keV, by conservation of energy. (This upper limit corresponds to the 

electron coming to a stop by emitting just one X-ray photon. Usually the 

electron emits many photons, and each has an energy less than 60 keV.) A 

photon with energy of at most 60 keV has wavelength of at least 21 pm, so 

the continuous X-ray spectrum has exactly that cutoff, as seen in the graph. 

More generally the formula for the low-wavelength cutoff is 


Spectrum of the X-rays emitted by an X-ray tube with a rhodium target, 

operated at 60 kV. The continuous curve is due to bremsstrahlung, and the 

spikes are characteristic K lines for rhodium. The curve goes to zero at 21 pm 

in agreement with the Duane–Hunt law, as described in the text. 




Characteristic & Bremsstrahlung Radiations 


Bremsstrahlung, from bremsen "to brake" and Strahlung "radiation", i.e. 

"braking radiation" or "deceleration radiation") is electromagnetic radiation 

produced by the deceleration of a charged particle when deflected by another 

charged particle, typically an electron by an atomic nucleus. The moving 

particle loses kinetic energy, which is converted into a photon, thus satisfying 

the law of conservation of energy. The term is also used to refer to the 

process of producing the radiation. Bremsstrahlung has a continuous 

spectrum, which becomes more intense and whose peak intensity shifts 

toward higher frequencies as the change of the energy of the accelerated 

particles increases. 

Broadly speaking, Bremsstrahlung or "braking radiation" is any radiation 

produced due to the deceleration (negative acceleration) of a charged particle, 

which includes synchrotron radiation, cyclotron radiation, and the emission of 

electrons and positrons during beta decay. However, the term is frequently 

used in the more narrow sense of radiation from electrons (from whatever 

source) slowing in matter. 



Elastic scattering 

Elastic scattering is a form of particle scattering in scattering theory, nuclear 

physics and particle physics. In this process, the kinetic energy of a particle is 

conserved in the center-of-mass frame, but its direction of propagation is 

modified (by interaction with other particles and/or potentials). 

Furthermore, while the particle's kinetic energy in the center-of-mass frame is 

constant, its energy in the lab frame is not. Generally, elastic scattering 

describes a process where the total kinetic energy of the system is conserved. 

During elastic scattering of high-energy subatomic particles, linear energy 

transfer (LET) takes place until the incident particle's energy and speed has 

been reduced to the same as its surroundings, at which point the particle is 

"stopped." 


Electron elastic scattering 

When an alpha particle is an incident particle and it is diffracted in the 

Coulomb potential of atoms and molecules, the elastic scattering process is 

called Rutherford scattering. In many electron diffraction techniques like 

reflection high energy electron diffraction (RHEED), transmission electron 

diffraction (TED), and gas electron diffraction (GED), where the incident 

electrons have sufficiently high energy (>10 keV), the elastic electron 

scattering becomes the main component of the scattering process and the 

scattering intensity is expressed as a function of the momentum transfer 

defined as the difference between the momentum vector of the incident 

electron and that of the scattered electron. 


Pictorial description of how an electron beam 

may interact with a sample with nucleus N, 

and electron cloud of electron shells K,L,M. 

Showing transmitted electrons and 

elastic/inelastic-ally scattered electrons. 

SE is a Secondary Electron ejected by the 

beam electron, emitting a characteristic 

photon (X-Ray) γ. BSE is a Back-Scattered 

Electron, an electron which is scattered 

backwards instead of being transmitted 

through the sample. 


Bremsstrahlung, from bremsen "to brake" and Strahlung "radiation", i.e. 

"braking radiation" or "deceleration radiation") is electromagnetic radiation 

produced by the deceleration of a charged particle when deflected by another 

charged particle, typically an electron by an atomic nucleus. 

Inelastic or elastic 

scattering 


■ Neutrons are typically produced by one of three methods. Large amounts of 

neutrons are produced in nuclear reactors due to the nuclear fission process. 

■ High energy neutrons are also produced by accelerating deuterons that 

causes them to interact with tritium nuclei. 

D + T → n + 4He En = 14.1 MeV 

D + D → n + 3He En = 2.5 MeV 


Nuclear physicist at the Idaho National Laboratory sets up an experiment using an 

electronic neutron generator. 


https://en.wikipedia.org/wiki/Neutron_generator

■ The third method of producing neutrons is by bombarding beryllium with 

alpha particles. Neutron sources can be made using the alpha-neutron 

reaction on beryllium by making a mixture of powered alpha emitter and 

beryllium and sealing it in a metal container. Early neutron sources used 

radium as the alpha emitter. Modern neutron sources typically use plutonium 

or americium as the alpha source. The radium-beryllium (Ra/Be) sources 

were also sources of large amounts of gamma radiation while the plutoniumberyllium 

(Pu/Be) sources and the americium-beryllium (Am/Be) sources only 

produce small amounts of very low energy gamma radiation. Thus, as 

neutron sources, Pu/Be and Am/Be sources tend to be less hazardous to 

handle. The older Ra/Be sources also had a tendency to develop leaks over 

time and give off radon gas, one of the products of radium decay. 

注 : Ra/Be - Ra as 4 2 He2+ source, Be as alpha target 


http://www-outreach.phy.cam.ac.uk/camphy/neutron/neutron5_1.htm

4 

2 He 2+ + 9 4 Be → 12 6 C + n 


http://www-outreach.phy.cam.ac.uk/camphy/neutron/5_neutron.swf

4 

2 He 2+ + 9 4 Be → 12 6 C + n http://www-outreach.phy.cam.ac.uk/camphy/neutron/neutron5_1.htm 


4 

2 He 2+ + 9 4 Be → 12 6 C + n http://www-outreach.phy.cam.ac.uk/camphy/neutron/neutron5_1.htm 


Ionizing Radiation - Interaction with Matter 

As ionizing radiation moves from point to point in matter, it loses its energy 

through various interactions with the atoms it encounters. The rate at which 

this energy loss occurs depends upon the type and energy of the radiation 

and the density and atomic composition of the matter through which it is 

passing. 

The various types of ionizing radiation impart their energy to matter primarily 

through excitation and ionization of orbital electrons. The term "excitation" is 

used to describe an interaction where electrons acquire energy from a 

passing charged particle but are not removed completely from their atom. 

Excited electrons may subsequently emit energy in the form of x-rays during 

the process of returning to a lower energy state. The term "ionization" refers 

to the complete removal of an electron from an atom following the transfer of 

energy from a passing charged particle. In describing the intensity of 

ionization, the term "specific ionization" is often used. This is defined as the 

number of ion pairs formed per unit path length for a given type of radiation. 

Keywords: Excitation, Ionization, specific ionization. 


Because of their double charge and relatively slow velocity, alpha particles 

have a high specific ionization and a relatively short range in matter (a few 

centimeters in air and only fractions of a millimeter in tissue). Beta particles 

have a much lower specific ionization than alpha particles and, generally, a 

greater range. For example, the relatively energetic beta particles from P32 

have a maximum range of 7 meters in air and 8 millimeters in tissue. The low 

energy betas from H3, on the other hand, are stopped by only 6 millimeters of 

air or 6 micrometers of tissue 

"specific ionization" is often used. 

This is defined as the number of ion 

pairs formed per unit path length for a 

given type of radiation. 


Gamma-rays, x-rays, and neutrons are referred to as indirectly ionizing 

radiation since, having no charge, they do not directly apply impulses to 

orbital electrons as do alpha and beta particles. Electromagnetic radiation 

proceed through matter until there is a chance of interaction with a particle. If 

the particle is an electron, it may receive enough energy to be ionized, 

whereupon it causes further ionization by direct interactions with other 

electrons. As a result, indirectly ionizing radiation (e.g. gamma, x-rays, and 

neutrons) can cause the liberation of directly ionizing particles (electrons) 

deep inside a medium. Because these neutral radiations undergo only 

chance encounters with matter, they do not have finite ranges, but rather are 

attenuated in an exponential manner. In other words, a given gamma ray has 

a definite probability of passing through any medium of any depth. 

Keywords: 

directly ionizing radiation – Beta, Alpha particle. 

indirectly ionizing radiation – γ ray, X-ray, neutron particle. 


Neutrons lose energy in matter by collisions which transfer kinetic energy. 

This process is called moderation and is most effective if the matter the 

neutrons collide with has about the same mass as the neutron. 

Once slowed down to the same average energy as the matter being 

interacted with (thermal energies), the neutrons have a much greater chance 

of interacting with a nucleus. Such interactions can result in material 

becoming radioactive or can cause radiation to be given off. 


The quantity which expresses the degree of radioactivity or radiation 

producing potential of a given amount of radioactive material is activity. 

The concentration of radioactivity, or the relationship between the mass of 

radioactive material and the activity, is called "specific activity." Specific 

activity is expressed as the number of curies or becquerels per unit mass or 

volume. 

■ Each gram of Cobalt-60 will contain approximately 50 curies. 

■ Each gram of Iridium-192 will contain approximately 350 curies. 

The shorter half-life, the less amount of material that will be required to 

produce a given activity or curies. The higher specific activity of Iridium results 

in physically smaller sources This allows technicians to place the source in 

closer proximity to the film while maintaining geometric unsharpness 

requirements on the radiograph. These unsharpness requirements may not 

be met if a source with a low specific activity were used at similar source to 

film distances. 



Extra curriculum 


Neutron 


Quarks 

Neutrons and Protons – do they have a structure? 

As early as 1961 a paper appeared in Discovery magazine by Professor EHS 

Burhop of University College London suggesting that protons and neutrons 

were in fact not fundamental particles but that they had a structure. In 1964 

Murray Gell-Mann and George Zweig proposed that all hadrons (mesons and 

baryons) were composed of particles that they called QUARKS. 

These were finally discovered in 1975 and at the present time (2002) are 

thought to be the fundamental particles of matter. One of the most unusual 

properties of quarks is that they have fractional electric charge compared with 

the charge on the electron of -e. 

Their existence was confirmed by high energy electron scattering from the 

nucleons. 

There are actually six quarks and their anti-quarks but in every day life we are 

only concerned with three types: the up quark, the down quark and the 

strange quark. (other quarks are charm, top and bottom) 


http://schoolphysics.co.uk/age16-19/Nuclear%20physics/Nuclear%20structure/text/Quarks_/index.html

Properties of quarks 



Quarks in protons and neutrons 

It was found that quarks can only exit in threes in a proton or neutron. They 

are held together to form a larger particle by the strong force produced by the 

exchange of gluons between them. These particles contain three quarks. It 

has proved very difficult if not impossible to obtain an isolated quark. As you 

try to pull them out of the proton or neutron it gets more and more difficult. 

Even stranger is the suggestion that if you could pull a quark out of a proton it 

would immediately form a quark- antiquark pair and leave you with a quark 

inside the proton and nothing outside – status quo! 

The reason that it is impossible to get a quark "on its own" is because as you 

try to separate them from each other the energy needed gets greater and 

greater. In fact when they "break apart" the energy is sufficient to create two 

new antiquarks and these join to form pions and so the quarks "disappear"! 



Quark composition of baryons including the proton and the neutron 

All baryons and antibaryons are made up of three quarks. 

Proton: up up down uud charge = +2/3 +2/3 -1/3 = +1 

Neutron: down down up ddu charge = -1/3 -1/3 +2/3 = 0 



You must be careful that you are clear of what diagrams that show three 

quarks IN a proton or a neutron are supposed to explain. The three quarks 

ARE the proton or the neutron but the drawings just help to show this. 

Notice that electrons and neutrinos contain no quarks, they are themselves 

truly fundamental particles (or so we think at present) 

When you try and drag a quark out of a proton the strong force gets bigger 

and bigger – rather like the force in a spring as it is stretched. 

The "mass" of the up and down quarks is 360 MeV. Three of them in a proton 

gives a mass of 1080 MeV. The mass of the proton is around 930 MeV giving 

a sort of binding energy of 150 MeV. 



The quark nature of beta decay 

The quark nature of the proton and neutron can be used to explain beta decay. 



Quark version: 

In beta plus decay an up quark changes into down quark with the emission of 

a positron and a neutrino, while in beta minus decay a down quark changes 

into a up quark with the emission of an electron and an anti-neutrino. 

The quarks are held together in the nucleus by the strong nuclear force. This 

acts only over a very short range, around 10 -15 m and is also responsible for 

holding the neutrons and protons together in the nucleus. It is thought that the 

force is carried by the exchange of virtual particles called gluons! These are 

allowed to appear and disappear as long as they do not violate Heisenberg's 

uncertainty principle. 



This means that the particle can exist for a time of Δt as long as its energy is 

no greater than (h/2π)/Δt or more usefully it can have an energy of ΔE as 

long as it exits for less than (h/2π)/ΔE where h is Plank's constant 

(6.64x10 -34 Js). 

Additional note – mesons and baryons 

Baryons are composed of three quarks while mesons are composed of two 

quarks. One of the quarks in any meson is an anti-quark. For example a π+ 

meson is composed of one up quark and one anti-down quark. 



What is inside the nucleus? 

By 1910 the atom was thought to consist of a massive nucleus orbited by 

electrons, but measurements of atomic mass indicated that all nuclei must 

contain integer numbers of some other particle. What were these particles 

inside the nucleus? 

One of these particles was the proton. The proton was discovered during 

investigations of positive rays, and can be produced by ionising hydrogen. 

Hydrogen is the lightest type of atom, consisting of a single proton and a 

single electron. Ionisation separates the electron from the atom, so only the 

proton remains. 

If more massive nuclei contained only protons their charge would be much 

higher than measurements suggested. With the exception of hydrogen all 

atoms have a higher mass number than charge number. Rutherford thought 

that the nucleus consisted of protons and 'neutral doublets' formed from 

closely bound protons and electrons. This could explain both the mass and 

the charge that had been measured for different nuclei. 



Chadwick's neutron chamber 

containing parallel disks of radioactive polonium and beryllium. Radiation is 

emitted from an aluminium window at the chamber's end 

aluminium window 



James Chadwick (20 October 1891 – 24 July 1974) 


2. The elusive neutron 

Rutherford described his 'neutral doublet', or neutron, in 1920. The particle 

would be uncharged but with a mass only slightly greater than the proton. 

Because it was uncharged there would be no electrical repulsion of the 

neutron as it passed through matter, so it would be much more penetrating 

than the proton. This would make the neutron difficult to detect. 

The discovery of the neutron was made by James Chadwick, who spent more 

than a decade searching. Chadwick had accompanied Rutherford in his move 

from Manchester to Cambridge. He later became the Assistant Director of 

Research in the Cavendish, and was responsible for keeping Rutherford 

informed of any new developments in physics. Chadwick and Rutherford 

often discussed neutrons, and suggested 'silly' experiments to discover them, 

but the inspiration for Chadwick's discovery came from Europe, not 

Rutherford. 



Proton & Neutron Passing Thru Matters 



3. Beryllium radiation 

In 1930 the German physicists Bothe and Becker bombarded the light metal 

beryllium with alpha particles, and noticed that a very penetrating radiation 

was emitted. This radiation was non-ionising, and they assumed it was 

gamma rays. 

In 1932 Irène and Frédéric Joliot-Curie investigated this radiation in France. 

They let the radiation hit a block of paraffin wax, and found it caused the wax 

to emit protons. They measured the speeds of these protons and found that 

the gamma rays would have to be incredibly energetic to knock them from the 

wax. 

Chadwick reported the Joliot-Curie's experiment to Rutherford, who did not 

believe that gamma rays could account for the protons from the wax. He and 

Chadwick were convinced that the beryllium was emitting neutrons. Neutrons 

have nearly the same mass as protons, so should knock protons from a wax 

block fairly easily. 

4 

2 He 2+ + 9 4 Be → 12 6 C + 1 0 n0 http://www-outreach.phy.cam.ac.uk/camphy/neutron/neutron1_1.htm 


Ernest Rutherford 

http://www-outreach.phy.cam.ac.uk/camphy/neutron/neutron1_1.htm 


4. Chadwick's discovery 

Chadwick worked day and night to prove the neutron theory, studying the 

beryllium radiation with an ionisation counter and a cloud chamber. He found 

that the wax could be replaced with other light substances, even beryllium, 

and that protons were still produced. Within a month Chadwick had 

conclusive proof of the existence of the neutron. He published his findings in 

the journal, Nature, on February 27, 1932. 



Chadwick’s Experiment 



5. Neutrons from beryllium 

The alpha-particles from the radioactive source hit the beryllium nuclei and 

transformed them into carbon nuclei, leaving one free neutron. When this 

neutron hit the hydrogen nuclei in the wax it could knock a proton free, in the 

same way that a white snooker ball can transfer all its energy to a red 

snooker ball. 

Rutherford gave the best description of a neutron as a highly penetrating 

neutral particle with a mass similar to the proton. We now know it is not a 

combination of an electron and a proton. Quantum mechanics restricts an 

electron from getting that close to the proton, and measurements of nuclear 

'spin' provide experimental proof that the nucleus does not contain electrons. 



tank erections whereby 



6. The decaying particle 

Chadwick knew the neutron wasn't formed from an electron and a proton, and 

explained in his Nobel lecture that it seemed 'useless to discuss whether the 

neutron and proton are elementary particles or not'. He knew that a more 

powerful investigation of the neutron was necessary to decide if it was made 

up of anything else. We now believe that the neutron and the proton are 

made of even tinier particles called quarks. 

To further confuse matters, free neutrons are not stable. If a neutron is 

outside the nucleus for several minutes it will transform into a proton, an 

electron, and an extremely light particle called a neutrino. The decay occurs 

because one of the quarks inside the neutron has transformed into a different 

quark, producing an additional positive charge in the particle. 



7. The nuclear bomb 

Neutrons are very penetrating because they are uncharged. This makes them 

very useful to nuclear physicists, as they can be fired into the nucleus without 

being repelled like the proton. A neutron can even be made to stop inside a 

nucleus, transforming elements into more massive types. 

This understanding of the neutron allowed scientists to develop nuclear 

power, and nuclear weapons during the Second World War. Chadwick helped 

in the theory behind the first nuclear bombs, and used a particle accelerator in 

Liverpool to show that it is possible to construct them with only a few 

kilograms of uranium. 



This short video clip shows the 'Trinity' nuclear fission bomb, tested in the 

desert of New Mexico, USA on July 16, 1945. Three weeks later America 

dropped two similar bombs, using different fissile material, on Japan. The 

Trinity bomb was the first nuclear fission explosion on Earth and resulted in a 

blast that could be felt over 250 miles away. The Trinity bomb used plutonium 

as its fissile material, the same metal used in the bomb dropped on Nagasaki. 

The Hiroshima bomb used the slightly lighter metal uranium. 



Trinity Nuclear Fission Bomb 


http://nuclearweaponarchive.org/Usa/Tests/Trinity.html

http://www.dailymail.co.uk/news/article-2645299/Haunting-photographs-Nagasaki-wake-atomic-bomb-attack-used-Japanese-propaganda-stolen-U-S-soldier.html 








Reading is always fun! End of Reading 


The neutron is a subatomic particle, symbol n or n 0 , with no net electric 

charge and a mass slightly larger than that of a proton. Protons and neutrons, 

each with mass approximately one atomic mass unit, constitute the nucleus of 

an atom, and they are collectively referred to as nucleons. Their properties 

and interactions are described by nuclear physics. 

The nucleus consists of Z protons, where Z is called the atomic number, and 

N neutrons, where N is the neutron number. The atomic number defines the 

chemical properties of the atom, and the neutron number determines the 

isotope or nuclide. The terms isotope and nuclide are often used 

synonymously, but they refer to chemical and nuclear properties, respectively. 

The atomic mass number, symbol A, equals Z+N. For example, carbon has 

atomic number 6, and its abundant carbon-12 isotope has 6 neutrons, 

whereas its rare carbon-13 isotope has 7 neutrons. Some elements occur in 

nature with only one stable isotope, such as fluorine. Other elements occur as 

many stable isotopes, such as tin with ten stable isotopes. Even though it is 

not a chemical element, the neutron is included in the table of nuclides. 


Within the nucleus, protons and neutrons are bound together through the 

nuclear force, and neutrons are required for the stability of nuclei. Neutrons 

are produced copiously in nuclear fission and fusion. They are a primary 

contributor to the nucleosynthesis of chemical elements within stars through 

fission, fusion, and neutron capture processes. 

The neutron is essential to the production of nuclear power. In the decade 

after the neutron was discovered in 1932, neutrons were used to effect many 

different types of nuclear transmutations. With the discovery of nuclear fission 

in 1938, it was quickly realized that, if a fission event produced neutrons, 

each of these neutrons might cause further fission events, etc., in a cascade 

known as a nuclear chain reaction. These events and findings led to the first 

self-sustaining nuclear reactor (Chicago Pile-1, 1942) and the first nuclear 

weapon (Trinity, 1945). 


Free neutrons, or individual neutrons free of the nucleus, are effectively a 

form of ionizing radiation, and as such, are a biological hazard, depending 

upon dose. A small natural "neutron background" flux of free neutrons exists 

on Earth, caused by cosmic ray showers, and by the natural radioactivity of 

spontaneously fissionable elements in the Earth's crust. Dedicated neutron 

sources like neutron generators, research reactors and spallation sources 

produce free neutrons for use in irradiation and in neutron scattering 

experiments. 


Chapter 2: Newton's Inverse Square Law 

Any point source which spreads its influence equally in all directions 

without a limit to its range will obey the inverse square law. This comes from 

strictly geometrical considerations. The intensity of the influence at any given 

radius (r) is the source strength divided by the area of the sphere. Being 

strictly geometric in its origin, the inverse square law applies to diverse 

phenomena. Point sources of gravitational force, electric field, light, sound, or 

radiation obey the inverse square law. As one of the fields which obey the 

general inverse square law, a point radiation source can be characterized by 

the diagram above whether you are talking about Roentgens, rads, or rems. 

All measures of exposure will drop off by the inverse square law. For example, 

if the radiation exposure is 100 mR/hr at 1 inch from a source, the exposure 

will be 0.01 mR/hr at 100 inches. 


Inverse Square Law 


Isotope Decay Rate 

Gamma-rays are electromagnetic radiation emitted by the disintegration of a 

radioactive isotope and have energy from about 100 keV to well over 1 MeV, 

corresponding to about 0.01 to 0.001 Å. The most useful gamma-emitting 

radioactive isotopes for radiological purposes are found to be cobalt (Co60), 

iridium (Ir192), cesium (Cs137), ytterbium (Yb169), and thulium (Tm170). 

N(t) = N o e –λt 

Decay Rate: 

When t = 0 

• dN/dt ∝N 

• dN/dt = -λN 

• ∫dN/N = ∫-λdt 

• ln N +C’ = -λt + C″ 

• ln N = -λt + C 

• N = No = e C 

• N = N o e -λt 

• When N=1/2No, t= T½ 

• 0.5 = e –λT ½ 

• ln 0.5 = –λT ½ 

• N = e -λt ·e C • λ = 0.693/T ½ 

• N = N o e -0.693t/T½ 

http://chemwiki.ucdavis.edu/Core/Physical_Chemistry/Nuclear_Chemistry/Radioactivity/Radioactive_Decay_Rates 


Carbon-14 Dating 


Radio-carbon dating is a method of obtaining age estimates on organic 

materials which has been used to date samples as old as 50,000 years. The 

method was developed immediately following World War II by Willard F. Libby 

and coworkers and has provided age determinations in archeology, geology, 

geophysics, and other branches of science. Radiocarbon determinations can 

be obtained on wood, charcoal, marine and freshwater shell, bone and antler, 

and peat and organic-bearing sediments. They can also be obtained from 

carbonate deposits such as tufa, calcite, marl, dissolved carbon dioxide, and 

carbonates in ocean, lake and groundwater sources. 

Each sample type has specific problems associated with its use for dating 

purposes, including contamination and special environmental effects. While 

the impact of radiocarbon dating has been most profound in archeological 

research and particularly in prehistoric studies, extremely significant 

contributions have also been made in hydrology and oceanography. In 

addition, in the 1950's the testing of thermonuclear weapons injected large 

amounts of artificial radiocarbon ("Radiocarbon Bomb") into the atmosphere, 

permitting it to be used as a geochemical tracer. 


Carbon dioxide is distributed on a worldwide basis into various atmospheric, 

biospheric, and hydrospheric reservoirs on a time scale much shorter than its 

half-life. Metabolic processes in living organisms and relatively rapid turnover 

of carbonates in surface ocean waters maintain radiocarbon levels at 

approximately constant levels in most of the biosphere. 

Most living organisms absorb carbon. During its lifetime, an organism 

continually replenishes its supply of carbon just by breathing and eating. 

Carbon (C) has three naturally occurring isotopes. Both C-12 and C-13 are 

stable, but C-14 decays by very weak beta decay to nitrogen-14 with a halflife 

of approximately 5,730 years. Naturally occurring Radiocarbon is 

produced as a secondary effect of cosmic-ray bombardment of the upper 

atmosphere. 


After the organism dies and becomes a fossil, Carbon-14 continues to decay 

without being replaced. To measure the amount of radiocarbon left in a fossil, 

scientists burn a small piece to convert it into carbon dioxide gas. Radiation 

counters are used to detect the electrons given off by decaying C-14 as it 

turns into nitrogen. The amount of C-14 is compared to the amount of C-12, 

the stable form of carbon, to determine how much radiocarbon has decayed, 

therefore, dating the fossil. 

N = N o e -λt = N o e -0.693t/T½ 

Where “N" is the present amount of the radioactive isotope, “N o " is the original 

amount of the radioactive isotope that is measured in the same units as "A." 

"t" is the time it takes to reduce the original amount of the isotope to the 

present amount, and “ T ½ " is the half-life of the isotope, measured in the same 

units as "t." 


t has long been recognized that if radiocarbon atoms could be detected 

directly, rather than by waiting for their decay, smaller samples could be used 

for dating and older dates could be measured. A simple hypothetical example 

to illustrate this point is a sample containing only one atom of radiocarbon. To 

measure the age (that is, the abundance of radiocarbon), the sample can be 

placed into a mass spectrometer and that atom counted, or the sample can 

be placed into a Geiger counter and counted, requiring a wait on the average 

of 8,000 years (the mean life of radiocarbon) for the decay. In practice, 

neither the atoms nor the decays can be counted with 100% efficiency. 


Chapter 3 Interaction Between Penetrating 

Radiation and Matter 

Interaction between penetrating radiation and matter is not a simple process 

in which the primary x-ray photon changes to some other form of energy and 

effectively disappears. The diagram below shows the absorption coefficient, µ, 

for four radiation-matter interactions as a function of radiation energy in MeV. 

The graph is representative of radiation interacting with Iron. Absorption will 

be covered in greater detail in a later page. 


Summary of different mechanisms that reduce 

intensity of an incident x-ray beam 

Photoelectric (PE) absorption of x-rays occurs when the x-ray photon is 

absorbed resulting in the ejection of electrons from the outer shell of the atom, 

resulting in the ionization of the atom. Subsequently, the ionized atom returns 

to the neutral state with the emission of an x-ray characteristic of the atom. 

This subsequent emission of lower energy photons is generally absorbed and 

does not contribute to (or hinder) the image making process. Photoelectron 

absorption is the dominant process for x-ray absorption up to energies of 

about 500 KeV. Photoelectron absorption is also dominant for atoms of high 

atomic numbers. 


Photoelectric 


Pair Production (PP) can occur when the x-ray photon energy is greater 

than 1.02 MeV, when an electron and positron are created with the 

annihilation of the x-ray photon. Positrons are very short lived and disappear 

(positron annihilation) with the formation of two photons of 0.51 MeV energy. 

Pair production is of particular importance when high-energy photons pass 

through materials of a high atomic number. Energy: > 1.02 MeV 


Compton Scattering (C), also known a incoherent scattering, occurs when 

the incident x-ray photon ejects a electron from an atom and an x-ray photon 

of lower energy is scattered from the atom. Relativistic energy and 

momentum are conserved in this process (demonstrated in the applet below) 

and the scattered x-ray photon has less energy and therefore greater 

wavelength than the incident photon. Compton Scattering is important for low 

atomic number specimens. At energies of 100 keV -- 10 MeV the absorption 

of radiation is mainly due to the Compton effect. 


Together with the scattering of photons on free electrons, the photoelectric 

effect, and pair production, Compton scattering contributes to the attenuation 

of x-rays in matter. As the binding energy of electrons in atoms is low 

compared to that of passing near-relativistic particles, this is the relevant 

process in radiography. Closely related are Thompson scattering (classical 

treatment of photon scattering) and Rayleigh scattering (coherent scattering 

on atoms). 

Compton Scattering, also known as incoherent scattering, occurs when the 

incident x-ray photon ejects a electron from an atom and an x-ray photon of 

lower energy is scattered from the atom. Relativistic energy and momentum 

are conserved in this process (demonstrated in the applet below) and the 

scattered x-ray photon has less energy and therefore a longer wavelength 

than the incident photon. Compton scattering is important for low atomic 

number specimens. 


Below are other interaction phenomenon that can occur. Under special 

circumstances these may need to be considered, but are generally negligible. 

Thomson scattering (R), also known as Rayleigh, coherent, or classical 

scattering, occurs when the x-ray photon interacts with the whole atom so that 

the photon is scattered with no change in internal energy to the scattering 

atom, nor to the x-ray photon. Thomson scattering is never more than a minor 

contributor to the absorption coefficient. The scattering occurs without the 

loss of energy. Scattering is mainly in the forward direction. 



http://www.mssl.ucl.ac.uk/www_astro/lecturenotes/hea/radprocess/sld001.htm

Idea of Cross Section: 

In nuclear and particle physics, the concept of a neutron cross section is used 

to express the likelihood of interaction between an incident neutron and a 

target nucleus. In conjunction with the neutron flux, it enables the calculation 

of the reaction rate, for example to derive the thermal power of a nuclear 

power plant. The standard unit for measuring the cross section is the barn, 

which is equal to 10 −28 m 2 or 10 −24 cm 2 . The larger neutron cross section, the 

more likely a neutron will react with the nucleus. 


Photodisintegration (PD) is the process by which the x-ray photon is 

captured by the nucleus of the atom with the ejection of a particle from the 

nucleus when all the energy of the x-ray is given to the nucleus. Because of 

the enormously high energies involved, this process may be neglected for the 

energies of x-rays used in radiography. 




http://www.kuwo.cn/yinyue/302998/


https://www.youtube.com/watch?v=3fLuPIPp0p4





Chapter 4 Absorption 

Absorption characteristics of materials are important in the development of 

contrast in a radiograph. Absorption characteristics will increase or decrease 

as the energy of the x-ray is increased or decreased. A radiograph with higher 

contrast will provide greater probability of detection of a given discontinuity. 

An understanding of the relationship between material thickness, absorption 

properties, and photon energy is fundamental to producing a quality 

radiograph. An understanding of absorption is also necessary when designing 

x- and gamma ray shielding, cabinets, or exposure vaults. 

Attenuation of x-rays in solids takes place by several different mechanisms, 

some due to absorption, others due to the scattering of the beam. Thompson 

scattering (also known as Rayleigh, coherent, or classical scattering) and 

Compton Scattering (also known as incoherent scattering) were introduced in 

the material titled "Interaction Between Penetrating Radiation and Matter" and 

"Compton Scattering." This needs careful attention because a good 

radiograph can only be achieved if there is minimum x-ray scattering. 


The figure below shows an approximation of the Absorption coefficient, µ, in 

red, for Iron plotted as a function of radiation energy. 


The attenuation or absorption, usually defined as the linear absorption 

coefficient, µ, is defined for a (1) narrow well-collimated, (2) monochromatic 

x-ray beam. The linear absorption coefficient is the sum of contributions of the 

following: 

1. Thomson scattering (R) (also known as Rayleigh, coherent, or classical 

scattering) occurs when the x-ray photon interacts with the whole atom so 

that the photon is scattered with no change in internal energy to the 

scattering atom, nor to the x-ray photon. 

2. Photoelectric (PE) absorption of x-rays occurs when the x-ray photon is 

absorbed resulting in the ejection of electrons from the outer shell (?) of 

the atom, resulting in the ionization of the atom. Subsequently, the ionized 

atom returns to the neutral state with the emission of an x-ray 

characteristic of the atom. 

3. Compton Scattering (C) (also known a incoherent scattering) occurs when 

the incident x-ray photon ejects an electron from an atom and a x-ray 

photon of lower energy is scattered from the atom. 


4. Pair Production (PP) can occur when the x-ray photon energy is greater 

than 1.02 MeV, when an electron and positron are created with the 

annihilation of the x-ray photon (absorption). 

5. Photodisintegration (PD) is the process by which the x-ray photon is 

captured by the nucleus of the atom with the ejection of a particle from the 

nucleus when all the energy of the x-ray is given to the nucleus 

(absorption). This process may be neglected for the energies of x-rays 

used in radiography. (>10Mev?) 


A narrow beam of monoenergetic photons with an incident intensity Io, 

penetrating a layer of material with mass thickness x and density p, emerges 

with intensity I given by the exponential attenuation law, 

I/I o = e -(µ/p)x 

which can be rewritten as: 

µ/p = ln(I o /I)/x 

from which can be obtained from measured values of I o , I and x. Note that the 

mass thickness is defined as the mass per unit area, and is obtained by 

multiplying the thickness t by the density, i.e., x = t. These conditions, 

generally do not apply to radiography. Scattered x-rays leave the beam and 

and contribute to the decrease in intensity. 


Geometry and X-ray Resolution 

Source to film distance, object to film distance, and source size directly affect the 

degree of penumbra shadow and geometric unsharpness of a radiograph. Codes and 

standards used in industrial radiography require that geometric unsharpness be 

limited. 

The three factors controlling unsharpness are source size, source to object distance, 

and object to detector distance. The source size is obtained by referencing 

manufacturers specifications for a given x- or gamma ray source. Industrial x-ray 

tubes often have source (anode) sizes of 1.5 mm 2 . A balance must be maintained 

between duty cycle, killovoltage applied, and source size. X-ray sources (anodes) may 

be reduced to sizes as small as microns for special applications. As the source (anode) 

size is increased or decreased, distance to the object can be increased or decreased 

and geometric unsharpness will remain constant. Source to object distance is primarily 

dependent on source size. Object to detector (object to film) distance is maintained as 

close as the particle. If the object is suspended above the detector an increase in 

unsharpness will result. Another result of the object being some distance from the film 

is geometric enlargement. This technique is used on small components. Industrial 

radiographers will use an externally small source and the object suspended above the 

detector that produces an enlarged image on the radiograph. Radiography of 

transistors and computer chips is one application of this technique. 





Additionally, it is generally 

accepted that an x-ray beam's 

intensity is not uniform throughout 

its entirety. Illustrated at the right, 

as x-radiation is emitted from the 

target area in a conical shape, 

measurements have determined 

that the intensity in the direction of 

the anode (AC) is lower (over and 

above the difference caused by the 

Inverse Square Law) 

anode 

C A B 

than the intensity in the direction of the cathode (AB). The fact that the 

intensities vary in such a manner causes visible differences in the density 

produced on the radiographs. This phenomenon is called heel effect. 

Radiographers should be aware of this phenomenon as codes require a 

minimum density through the area of interest. On low density radiographs the 

heal effect could cause a portion of the radiograph to not meet these 

requirements. 


The decreased intensity at "C" results from emission which is nearly parallel 

to the angled target where there is increasing absorption of the x-ray photons 

by the target itself (?) . This phenomenon is readily apparent in rotating anode 

tubes because they utilize steeply angled anodes of generally 17 degrees or 

less. Generally, the steeper the anode, the more severe or noticeable the 

heel effect becomes. 

The greater the focus film distance, the less noticeable the heel effect due to 

the smaller cone of radiation used to cover a given area. Heel effect is less 

significant on small films. This is due to the fact that the intensity of an x-ray 

beam is much more uniform near the central ray. 


C 

A 

B 


Rotating Anode Tube 


http://www.orau.org/ptp/collection/xraytubescoolidge/xraytubescoolidge.htm


http://www.orau.org/ptp/collection/xraytubescoolidge/xraytubescoolidge.htm

Filters in Radiography 

At x-ray energies, filters consist of material placed in the useful beam to 

absorb, preferentially, radiations based on energy level or to modify the 

spatial distribution of the beam. Filtration is required to absorb the lowerenergy 

x-ray photons emitted by the tube before they reach the target. The 

use of filters produce a cleaner image by absorbing the lower energy x-ray 

photons that tend to scatter more. 

The total filtration of the beam includes the inherent filtration (composed of 

part of the x-ray tube and tube housing) and the added filtration (thin sheets 

of a metal inserted in the x-ray beam). Filters are 

typically placed at or near the x-ray port in the direct 

path of the x-ray beam. Placing a thin sheet of 

copper between the part and the film cassette has 

also proven an effective method of filtration. 


For industrial radiography, the filters added to the x-ray beam are most often 

constructed of high atomic number materials such as lead, copper, or brass. 

Filters for medical radiography are usually made of aluminum (Al). The 

amount of both the inherent and the added filtration are stated in mm of Al or 

mm of Al equivalent. The amount of filtration of the x-ray beam is specified by 

and based on the kVp used to produce the beam. The thickness of filter 

materials is dependent on atomic numbers, kilovoltage settings, and the 

desired filtration factor. 

Gamma radiography 

produces relatively high 

energy levels at essentially 

monochromatic radiation, 

therefore filtration is not a 

useful technique and is 

seldom used. 



Secondary (Scatter) Radiation and Undercut Control 

Secondary or scatter radiation must often be taken into consideration when 

producing a radiograph. The scattered photons create a loss of contrast and 

definition. Often secondary radiation is thought of as radiation striking the film 

reflected from an object in the immediate area, such as a wall, or from the 

table or floor where the part is resting. Side scatter originates from walls, or 

objects on the source side of the film. Control of side scatter can be achieved 

by moving objects in the room away from the film, moving the x-ray tube to 

the center of the vault, or placing a collimator at the exit port thus reducing the 

diverging radiation surrounding the central beam. 



It is often called back scatter when it comes from objects behind the film. 

Industry codes and standards often require that a lead letter "B" be placed on 

the back of the cassette to verify the control of back scatter. If the letter "B" 

shows as a “ light ghost" image on the film the letter has absorbed the back 

scatter radiation indicating a significant amount of radiation reaching the film. 

Control of back scatter radiation is achieved by backing the film in the 

cassette with sheets of lead typically 0.010 inch thick. 

It is a common practice in industry to place 0.005 lead screen in front and 

0.010 backing the film. 


Back Scatter 


https://www.nde-ed.org/TeachingResources/teachingresources.htm

Undercut 

Another condition that must often be controlled when producing a radiograph 

is called undercut. Parts with holes, hollow areas, or abrupt thickness 

changes are likely to suffer from undercut if controls are not put in place. 

Undercut appears as lightening of the radiograph in the area of the thickness 

transition. This results in a loss of resolution or blurring at the transition area. 

Undercut occurs due to scattering within the film. At the edges of a part or 

areas where the part transitions from thick to thin, the intensity of the radiation 

reaching the film is much greater than in the thicker areas of the part. The 

high level of radiation intensity reaching the film results in a high level of 

scattering within the film. It should also be noted that the faster the film speed, 

the more undercut that is likely to occur. Scattering from within the walls of 

the part also contributed some to undercut but research has shown that 

scattering within the film is the primary cause. Masks are used to control 

undercut. Sheets of lead cut to fill holes or surround the part and metallic shot 

and liquid absorbers are often used as masks. 


Undercut 


Radiation Safety 


Radiation Safety 

Radionuclides in various chemical and physical forms have become 

extremely important tools in modern research. The ionizing radiation emitted 

by these materials, however, can pose a hazard to human health. For this 

reason, special precautions must be observed when radionuclides are used. 

The possession and use of radioactive materials in the United States is 

governed by strict regulatory controls. The primary regulatory authority for 

most types and uses of radioactive materials is the federal Nuclear 

Regulatory Commission (NRC). However, more than half of the states in the 

US (including Iowa) have entered into "agreement" with the NRC to assume 

regulatory control of radioactive material use within their borders. As part of 

the agreement process, the states must adopt and enforce regulations 

comparable to those found in Title 10 of the Code of Federal Regulations. 

Regulations for control of radioactive material use in Iowa are found in 

Chapter 136C of the Iowa Code. 


For most situations, the types and maximum 

quantities of radioactive materials possessed, 

the manner in which they may be used, and the 

individuals authorized to use radioactive 

materials are stipulated in the form of a 

"specific" license from the appropriate 

regulatory authority. In Iowa, this authority is the 

Iowa Department of Public Health. However, for 

certain institutions which routinely use large 

quantities of numerous types of radioactive 

materials, the exact quantities of materials and 

details of use may not be specified in the 

license. 

Instead, the license grants the institution the authority and responsibility 

for setting the specific requirements for radioactive material use within its 

facilities. These licensees are termed "broadscope" and require a 

Radiation Safety Committee and usually a full-time Radiation Safety 

Officer. 


The quantity which expresses the degree of radioactivity or radiation 

producing potential of a given amount of radioactive material is activity. The 

special unit for activity is the curie (Ci) which was originally defined as that 

amount of any radioactive material which disintegrates at the same rate as 

one gram of pure radium. The curie has since been defined more precisely as 

a quantity of radioactive material in which 3.7 x 10 10 atoms disintegrate per 

second. 

The International System (SI) unit for activity is the becquerel (Bq), which is 

that quantity of radioactive material in which one atom is transformed per 

second. The activity of a given amount of radioactive material not depend 

upon the mass of material present. For example, two one-curie sources of 

Cs-137 might have very different masses depending upon the relative 

proportion of non radioactive atoms present in each source. The 

concentration of radioactivity, or the relationship between the mass of 

radioactive material and the activity, is called the specific activity. Specific 


volume. 


The concentration of radioactivity, or the relationship between the mass of 

radioactive material and the activity, is called the specific activity. Specific 


volume. 



Chapter 5 Radiation Safety 

Radionuclides in various chemical and physical forms have become 

extremely important tools in modern research. The ionizing radiation emitted 

by these materials, however, can pose a hazard to human health. For this 

reason, special precautions must be observed when radionuclides are used. 

The possession and use of radioactive materials in the United States is 

governed by strict regulatory controls. The primary regulatory authority for 

most types and uses of radioactive materials is the federal Nuclear 

Regulatory Commission (NRC). However, more than half of the states in the 

US (including Iowa) have entered into "agreement" with the NRC to assume 

regulatory control of radioactive material use within their borders. As part of 

the agreement process, the states must adopt and enforce regulations 

comparable to those found in Title 10 of the Code of Federal Regulations. 

Regulations for control of radioactive material use in Iowa are found in 

Chapter 136C of the Iowa Code. 



ABSORBED DOSE - RAD (Radiation Absorbed Dose) 

The absorbed dose is the quantity that expresses the amount of energy which 

ionizing radiation imparts to a given mass of matter. 

1. The special unit for absorbed dose is the RAD (Radiation Absorbed Dose), 

which is defined as a dose of 100 ergs of energy per gram of matter. 

2. The SI unit for absorbed dose is the gray (Gy), which is defined as a dose 

of one joule per kilogram. 

3. Since one joule equals 10 7 ergs, and since one kilogram equals 1000 

grams, 1 Gray equals 100 rads. 

The size of the absorbed dose is dependent upon the strength (or activity) of 

the radiation source, the distance from the source to the irradiated material, 

and the time over which the material is irradiated. The activity of the source 

will determine the dose rate which can be expressed in rad/hr, mrad/hr, 

mGy/sec, etc. (mGy/sec/m?) 



DOSE EQUIVALENT - REM (Roentgen Equivalent Man) 

Although the biological effects of radiation are dependent upon the absorbed 

dose, some types of particles produce greater effects than others for the 

same amount of energy imparted. For example, for equal absorbed doses, 

alpha particles may be 20 times as damaging as beta particles. In order to 

account for these variations when describing human health risk from radiation 

exposure, the quantity called dose equivalent is used. This is the absorbed 

dose multiplied by certain "quality" and "modifying" factors (QF) indicative of 

the relative biological damage potential of the particular type of radiation. 

The special unit for dose equivalent is the rem (Roentgen Equivalent Man). 

The SI unit for dose equivalent is the sievert (Sv). 

Keywords: 

Rongent - dose rate for ionization of dry air at °C 

Rad (Gray) – dose rate of ionization of 1 joule per kilogram (tissue? Or any 

matters?) 

Rem (Sievert) – Roentgen equivalent man 



X-ray Sources 

X-rays are just like any other kind of electromagnetic radiation. They can be 

produced in parcels of energy called photons, just like light. There are two 

different atomic processes that can produce X-ray photons. One is called 

Bremsstrahlung and is a German term meaning "braking radiation." The other 

is called K-shell emission (L-shell?) . They can both occur in the heavy atoms 

of tungsten. Tungsten is often the material chosen for the target or anode of 

the x-ray tube. 


Both ways of making X-rays involve a change in the state of electrons. 

However, Bremsstrahlung is easier to understand using the classical idea that 

radiation is emitted when the velocity of the electron shot at the tungsten 

changes. The negativity charged electron slows down after swinging around 

the nucleus of a positively charged tungsten atom. This energy loss produces 

X-radiation. Electrons are scattered elastically and inelastically by the 

positively charged nucleus. The inelastically scattered electron loses energy, 

which appears as Bremsstrahlung. Elastically scattered electrons (which 

include backscattered electrons) are generally scattered through larger 

angles. In the interaction, many photons of different wavelengths are 

produced, but none of the photons have more energy than the electron had to 

begin with. After emitting the spectrum of X-ray radiation the original electron 

is slowed down or stopped. 


Bremsstrahlung Radiation 

X-ray tubes produce x-ray photons by 

accelerating a stream of electrons to 

energies of several hundred kilovolts with 

velocities of several hundred kilometers per 

hour and colliding them into a heavy target 

material. The abrupt acceleration of the 

charged particles (electrons) produces 

Bremsstrahlung photons. X-ray radiation 

with a continuous spectrum of energies is 

produced ranging from a few keV to a 

maximum of energy of the electron beam. 

Target materials for industrial tubes are typically tungsten, which means that 

the wave functions of the bound tungsten electrons are required. The 

inherent filtration of an X-ray tube must be computed, this is controlled by the 

amount that the electron penetrates into the surface of the target and by the 

type of vacuum window present. 


The bremsstrahlung photons generated within the target material are 

attenuated as they pass out through typically 50 microns of target material. 

The beam is further attenuated by the aluminum or beryllium vacuum window. 

The results are an elimination of the low energy photons, 1 keV through 

15keV, and a significant reduction in the portion of the spectrum from 15 keV 

through 50 keV. The spectrum from an x-ray tube is further modified by the 

filtration caused by the selection of filters used in the setup. 



http://hyperphysics.phy-astr.gsu.edu/%E2%80%8Chbase/quantum/xtube.html



K-shell emission Radiation 

Remember that atoms have their electrons arranged in closed "shells" of 

different energies. The K-shell is the lowest energy state of an atom. An 

incoming electron can give a K-shell electron enough energy to knock it out of 

its energy state. About 0.1% of the (incoming accelerated – cathode ray) 

electrons produce K-shell vacancies; most (99.9%) produce heat. Then, a 

tungsten electron of higher energy (from an outer shell) can fall into the K- 

shell. The energy lost by the falling electron shows up in an emitted x-ray 

photon. Meanwhile, higher energy electrons fall into the vacated energy state 

in the outer shell, and so on. K-shell emission produces higher-intensity x- 

rays than Bremsstrahlung, and the x-ray photon comes out at a single 

wavelength. 


K-shell emission Radiation 


When outer-shell electrons drop into inner shells, they emit a quantized 

photon "characteristic" of the element. The energies of the characteristic X- 

rays produced are only very weakly dependent on the chemical structure in 

which the atom is bound, indicating that the nonbonding shells of atoms are 

the X-ray source. The resulting characteristic spectrum is superimposed on 

the continuum as shown in the graphs below. An atom remains ionized for a 

very short time (about 10E-14 second) and thus an atom can be repeatedly 

ionized by the incident electrons which arrive about every 10E-12 second. 





X-ray Interactions with Matters 

Q1: In which process is matter converted back to energy? 

a. nuclear reaction 

b. annihilation reaction 

c. Compton scatter 

d. photodisintegration 

b. annihilation reaction (part of pair production interaction) 


https://quizlet.com/23654671/x-ray-interactions-flashcards-physics-flash-cards/

Q2: Which of the following interactions has a significant impact on the x-ray 

image? 

a. Compton scattering 

b. coherent scatter 

c. pair production 



Q3: Which of the following interactions with matter results in a radiograph with 

a long scale of contrast? 


b. coherent scatter 

c. photoelectric interactions 





Q4: As the angle of deflection is increased from 0º to 180º, ____. 

a. all energy is imparted to the incident photon 

b. less energy is imparted to the recoil electron 

c. greater energy is imparted to the scattered photon 

d. greater energy is imparted to the recoil electron 

d. greater energy is imparted to the recoil electron 

Q5: When x-ray photons interact with matter and change direction, the 

process is called ____. 

a. absorption 

b. scatter 

c. radiation 

d. binding energy 

b. scatter 



Q6: As the electrons shells move further from the nucleus, total electron 

energies ____ and binding energies ____. 

a. decrease, decrease 

b. increase, increase 

c. increase, decrease 

d. decrease, increase 

c. increase, decrease 

Q7: In which element are the inner shell electrons more tightly bound to the 

nucleus? 

a. mercury (Z = 80) 

b. tungsten (Z = 74) 

c. lead (Z = 82) 

d. chromium (Z = 24) 

c. lead (Z = 82) 



Q8: During the process of attenuation, ____ of x-ray photons in the beam. 

a. there is a reduction in the number 

b. there is a loss of energy 

c. there is an interaction 

d. all of the above 

d. all of the above 

Q9: When an x-ray passes through matter, it undergoes a process called 

____. 

a. radiation 

b. filtration 

c. attenuation 

d. fluoroscopy 

b. annihilation reaction 



Q10: If 5% of an incident beam is transmitted through a body part, then 95% 

of that beam was 

a. scattered. 

b. attenuated. 

c. absorbed. 

d. back-scattered. 

b.attenuated. 

Q11: At energies below 40 keV, the predominant x-ray interaction in soft 

tissue and bone is ____. 

a. coherent scatter 

b. Compton scatter 

c. photoelectric absorption 


c. photoelectric absorption 



Q12: High kVp techniques reduce 

a. patient dose. 

b. differential absorption. 

c. image fog. 

d. All of the above. 

a. patient dose. 

Q13: Compton interactions, photoelectric absorption, and transmitted x-rays 

all contribute to ____. 

a. image fog 

b. differential absorption 

c. patient dose 

d. attenuation 

b. differential absorption 



Q14: X-rays transmitted without interaction contribute to 

a. photoelectric absorption. 

b. the radiographic image. 

c. the image fog. 

d. beam attenuation. 

b. the radiographic image. 

Q15: A negative contrast agent is ____. 

a. air 

b. iodine 

c. barium 

d. water 

a. air 



Q16: The use of contrast agents increases the amount of 

a. differential absorption. 

b. Compton scatter. 

c. photoelectric absorption. 



Q17: Barium is a good contrast agent because of its 

a. low atomic number. 

b. high atomic number. 

c. light color. 

d. low density. 

b. high atomic number. 



Q18: Attenuation is caused by ____. 

a. absorption 

b. scattering 

c. transmission. 

d. Both a and b. 

d. Both a and b. 

Q19: Differential absorption is dependent on the 

a. kVp of the exposure. 

b. atomic number of the absorber. 

c. mass density of the absorber. 





Q20: Because of differential absorption, about ____ of the incident beam from 

the x-ray tube contributes to the finished image. 

a.0.5% 

b.10% 

c.50% 

d.95% 

a.0.5% 

Q21: Image fog in diagnostic imaging is caused by 

a. photoelectric absorption. 


c. pair production. 





Q22: Which has the greatest mass density? 

a. fat 

b. soft tissue 

c. bone 

d. air 

c. bone 

Q23: K-shell binding energy increases with increasing ____. 

a. mass density 

b. kVp 

c. atomic number 

d. mAs 

c. atomic number 



Q24: When the mass density of the absorber is ____, it results in ____ 

Compton scatter. 

a. decreased, increased 

b. increased, increased 

c. increased, decreased 

d. decreased, decreased 

b.increased, increased 

Q25: Only at energies above 10 MeV can ____ take place. 

a. photodisintegration 

b. pair production 

c. Compton scatter 

d. photoelectric absorption 

a. photodisintegration 



Q26: ____ occurs only at the very high energies used in radiation therapy and 

in nuclear medicine PET imaging. 

a. Coherent scatter 

b. Compton scatter 

c. Photoelectric absorption 

d. Pair production 

d.Pair production 

Q27: There is complete absorption of the incident x-ray photon with 

a. photoelectric effect. 

b. Compton interaction. 

c. pair production. 

d. coherent scatter. 

a. photoelectric effect. (pair production only if E = 1.02 Mev exactly) 



Q28: As kVp ____, the probability of photoelectric absorption ____. 

a. increases, remains the same 

b. increases, decreases 

c. decreases, decreases 

d. decreases, remains the same 

b. increases, decreases 

Q29: Compton scatter is directed at (a) ____ angle from the incident beam. 

a. 180º 

b. 90º 

c. 0º 

d. any 

d.any 



Q30: The scattered x-ray from a Compton interaction usually retains ____ of 

the energy of the incident photon. 

a. none 

b. little 

c. most 

d. all 

c. most 

Q31: Which x-ray interaction involves the ejection of the K-shell electron? 

a. coherent scattering 

b. Compton interaction 






Q32: The scattered x-ray from a Compton interaction usually retains ____ of 

the energy of the incident photon. 

a. none 

b. little 

c. most 

d. all 

c.most 

Q33: Which x-ray interaction involves the ejection of the K-shell electron? 

a. coherent scattering 

b. Compton interaction 






Q34: An outer-shell electron is ejected and the atom is ionized with 

a. photoelectric interactions. 

b. Compton interactions. 

c. coherent scattering. 

d. pair production. 

b. Compton interactions. 

Q35: An incident x-ray interacts with an atom without ionization during ____. 

a. photoelectric absorption 

b. Compton scattering 

c. coherent scattering 

d. pair production 

c.coherent scattering (momentarily no ionization?) 



Coherent scatter (or Thompson scatter) 

There are three main steps in coherent scatter. 

1. An incoming x ray photon with less than 10 keV (so a very low energy x 

ray photon) interacts with an outer orbital electron. 

2. The incoming x ray photon transfers ALL of its energy to the outer orbital 

electron. The incoming x ray photon no longer exists after transferring its 

energy. This makes the outer orbital electron excited. 

3. The outer orbital electron gives off the excess energy (in the form of an x 

ray photon) in a different direction than the original incoming x ray photon. 

The new x ray photon has the same energy as the incoming x ray photon. 


http://drgstoothpix.com/2012/10/17/attenuation-coherent-scatter/

Q36: The two primary forms of x-ray interaction in the diagnostic range are 

a. Compton scattering and photoelectric absorption. 

b. Compton scattering and pair production. 

c. photoelectric absorption and coherent scattering. 

d. coherent scattering and Thompson scattering. 

a. Compton scattering and photoelectric absorption. 



Marine Medic 


Marine Medic 


Q37: Coherent scattering 

Coherent scatter (or Thompson scatter) 

There are three main steps in coherent scatter. 

1. An incoming x ray photon with less than 10 keV (so a very low energy x ray photon) interacts with an outer 

orbital electron. 

2. The incoming x ray photon transfers ALL of its energy to the outer orbital electron. The incoming x ray 

photon no longer exists after transferring its energy. This makes the outer orbital electron excited. 

3. The outer orbital electron gives off the excess energy (in the form of an x ray photon) in a different direction 

than the original incoming x ray photon. The new x ray photon has the same energy as the incoming x ray 

photon. 

< 10 keV 



Q38: What happens to the x-ray in a Photoelectric effect? 

It is absorbs and disappears 

(the excess energy is converted into the kinetic energy of the free electron) 

Q39: What kvp is used to penetrate barium in a contrast examination? 

Approximately 90 kvp 



Q40: When the kvp is increased, what happens to the absolute probability of 

the photoelectric effect versus Compton effect? 

When kvp is increased the probability of any interaction is reduced but since 

the probability of PE interaction is reduced much more rapidly that the 

probability of Compton interaction the relative # of Compton interactions 

increases 



Q42: Of the five x-ray interactions with matter, three are not important to 

diagnostic radiology. Which are they and why are they not important? 

The x-ray energies of classical scattering, photo disintegration ,pair 

production are outside the energy range of diagnostic x-ray. 

Q42: What are the two factors of importance to differential absorption? 

Kev and atomic number of absorber 

Q43: A beam containing x-rays or gamma rays that all have the same energy 

monoenergetic 



Q44: Identify the x-ray interaction with matter 

Photodisintegration (PD) is the process by which the x-ray photon is captured 

by the nucleus of the atom with the ejection of a particle from the nucleus 

when all the energy of the x-ray is given to the nucleus. Because of the 

enormously high energies involved, this process may be neglected for the 

energies of x-rays used in radiography. 

Q45: A compound used as an aid for imaging internal organs with x-rays 

Contrast agent 

Q46: The absorption of an x-ray by ionization. 

Photoelectric effect 



Q47: The quantity of matter per unit volume 

Mass density 

Q48: Identify pair production. 

Photo 

Q49: Maximum differential absorption is possible with the use of _______kvp. 

low 

Q50: As the mass density of the absorber increases what effect does this 

have on the photoelectric effect? 

Proportional increase in PE 



Q51: As the atomic number is increased from Calcium Z #20 to Rhenium Z # 

45 what effect does this have on the PE? 

As atomic number of absorber increase the PE increases 

Increases proportionately with the cube of the atomic number (PE = KZ 3 ?) 

Q52: Increasing the kvp from 50 to 100 has what effect on the PE? 

As the kvp increases less PE and more Compton 

Q53: The interaction taking place with inner shell electrons is the__________. 

PE- Photoelectric effect 



Q54: What effect does increasing the energy level have on Compton 

scattering? 

Increased scatter relative to PE 

Increased penetration without interaction 

Q55: What effect does increasing the mass density of the absorber have on 

Compton scattering? 

A proportional increase in compton scattering 

Q56: What effect does atomic number of the absorber have on Compton 

scattering? 

No effect on Compton scattering 






Increases proportionately with the cube of the atomic number (PE = K·Z 4 ?) 


scattering? - No effect on Compton scattering 



Q57: Where in the atom does Compton scattering take place? 

Outer shell electrons 

Loosely bound electrons 

(As opposed to PE, the inner electrons?) 

Q58: ____ absorption results in the degree of contrast of an x-ray image 

Differential absorption 

Q59: Compton scattering _______ contrast in an x-ray image. 

reduces 

Q60: Total x-ray absorption effect 




Q61: A PE interaction is more likely to occur with a _____atomic number 

atoms . 

High 

Example 

Tungsten-74 

Lead- 82 

Barium-56 

Calcium-20 

Iodine-53 

Atomic nmber has no effect on compton scattering 

See 


scattering? - No effect on Compton scattering 



Q62: Identify the major source of radiation to the technologist. 

The majority of the radiation dose received by the operator is due to scattered 

radiation from the patient. After interacting with the patient, radiation is 

scattered more or less uniformly in all directions. 



Q63: Identify the x-ray interaction. 

Q64: Compton scattering 



Q65: What are the two electrons created by pair production called? 

Negatron & Positron 



Alpha Decay 


https://spec2000.net/06-atomicphysics.htm

Beta Decay 

N → P + e- + antineutrino 



Beta Decay 

P → P + e + + neutrino 



Q65: Pair production requires a photon energy of at least ______ mev. 

1.02 mev 

Q66: An interaction which occurs between low energy x-ray photons and 

matter 

Coherent scatter, classical scatter, unmodified scatter, Thomson scatter, 

Rayleigh scatter. 

Q67: When a scattered photon is deflected back toward the source it is called 

_______ radiation. 

Backscatter radiation 



Q68: _______ occurs when an incident x-ray photon interacts with a loosely 

bound outer shell electron, removes the electron from its shell and then 

proceeds in a different direction. 

Compton scattering 

Q69: The dislodged electron in a Compton interaction is called a ______. 

Compton electron 

Recoil electron 

Q70: How is the frequency of the x-ray photon affected by a Compton 

interaction? 

Lower frequency, some energy is lost. 



Q71: What affect does Compton scatter interaction have on the wavelength of 

the exiting scatter photon? 

Wavelength becomes longer, some energy is lost. 

Q72: What is the difference between Thomson and Rayleigh scatter radiation? 

Both are coherent scatter. Thomson involves a single electron in the 

interaction while Rayleigh scattering involves all of the electrons of the atom 

in the interaction. 

Q73: Coherent scattering occurs in a very ______ x-ray energy range, which 

is outside the diagnostic range. 

Low energy. Below 10 kev. 



Rayleigh Scattering 

Rayleigh scattering refers to the scattering of light off of the molecules of the 

air, and can be extended to scattering from particles up to about a tenth of the 

wavelength of the light. It is Rayleigh scattering off the molecules of the air 

which gives us the Blue sky. Lord Rayleigh calculated the scattered intensity 

from dipole scatterers much smaller than the wavelength to be: 


http://hyperphysics.phy-astr.gsu.edu/hbase/atmos/blusky.html

Rayleigh scattering can be considered to be elastic scattering since the 

photon energies of the scattered photons is not changed. Scattering in which 

the scattered photons have either a higher or lower photon energy is called 

Raman scattering. Usually this kind of scattering involves exciting some 

vibrational mode of the molecules, giving a lower scattered photon energy, or 

scattering off an excited vibrational state of a molecule which adds its 

vibrational energy to the incident photon. 

Thomson scattering is the elastic scattering of electromagnetic radiation by a 

free charged particle, as described by classical electromagnetism. It is just 

the low-energy limit of Compton scattering: the particle kinetic energy and 

photon frequency are the same before and after the scattering. This limit is 

valid as long as the photon energy is much less than the mass energy of the 

particle: Ѵ

• Low-energy phenomena: 


• Mid-energy phenomena: 

Thomson scattering 


• High-energy phenomena: 

Pair production 

Photondisintegration 


https://en.wikipedia.org/wiki/Thomson_scattering

Q74a: What three basic rules which govern the possibility of photoelectric 

interaction? 

1. The incident x-ray photon energy must be greater than the binding energy 

of the inner shell electron. 

2. The PE interaction is more likely to occur when the x-ray photon energy & 

the electron binding energy are nearer to one another. 

3. A PE is more likely to occur with an electron which is more tightly bound. 

Q74b: The term used for the reduction in the number of x-ray photons in the 

beam after it has passed thru matter. 

attenuation 

Q75: In pair production to photons are created each with an energy of 

____mev. 

0.51 mev. 



Q76: True or False: Pair production does not occur in the diagnostic range. 

True: Pair production requires 1.02 mev which is much higher energy than the 

diagnostic range. 

Q77: Interactions above 10 Mev are ________ interactions. 

photodisintegration 

Q78: Which interaction has a high energy photon strike the nucleus and all of 

its energy is absorbed by the nucleus causing a nuclear fragment to be 

emitted? 




Photodisintegration 


Photodisintegration 


Q79: True or False: Pair production does not occur in the diagnostic range. 

True: Pair production requires 1.02 mev which is much higher energy than the 

diagnostic range. 

Q80: Interactions above 10 Mev are ________ interactions. 


Q81: Which interaction has a high energy photon strike the nucleus and all of 

its energy is absorbed by the nucleus causing a nuclear fragment to be 

emitted? 




Q82: What affect does a high atomic number have on the binding energy of 

an element? 

Direct relationship. As the number of protons increases with increased atomic 

number the positive charges increase the binding energy making it more 

difficult to remove electrons from their shells. 

Q83: Which shell will have the highest energy? 

The shell furthest from the nucleaus. 

Q84: Which shell has the highest binding energy? 

Always the K-shell closest to the nucleus. 



Q85: List the 5 basic interactions between x-rays and matter. 

1. Photoelectric absorption 

2. Coherent scattering 

3. Compton scattering 

4. Pair production 

5. Photodisintegration 

Q86: Another name for the characteristic photon is ______ radiation. 

Secondary. 

Q87: What is the primary cause of occupational radiation exposure to 

radiographers? 

Scatter radiation emitted by the patient. 



Q88: ________ interaction the energy of the x-ray photon is converted to 

matter in the form of two electrons. 

Pair production. 

Q89: An electron with a positive charge. 

Position. 

Q90: Which of the five interactions has a significant impact on an x-ray image? 

Photoelectric-Compton 



Q91: What affect does increasing the kVp have on PE and Compton 

scattering? 

PE decreases with increasing kVp. Compton increases with increasing kVp 

requiring the use of a grid to clean up scatter. 

Q92: Which interaction is predominant in the human body in the diagnostic x- 

ray range? 


Q93: When the PE is more prevalent the resulting radiographic image will 

possess _______ contrast. 

High Contrast-Short scale contrast-Very black and white contrast. 



Q94: What affect does increasing the kVp have on PE and Compton 

scattering? 

PE decreases with increasing kVp. Compton increases with increasing kVp 

requiring the use of a grid to clean up scatter. 

Q95: Which interaction is predominant in the human body in the diagnostic x- 

ray range? 


Q96: When the PE is more prevalent the resulting radiographic image will 

possess _______ contrast. 

High Contrast-Short scale contrast-Very black and white contrast. 



Q97: High contrast images can be created by selecting _______ kVp and 

______ mAs. 

Low kVp and High mAs. 

Q98: Low contrast images are created by using ______ kVp and ______ mAs. 

High kVp and Low mAs. 

Q99: What is backscatter? 

When a scattered photon is deflected back toward the source, it is traveling in 

the opposite direction from the incident photon. 



Q100: Scattering of very low energy x-rays with no loss of energy care 

called________. 

Coherent scattering - Thompson scattering. 

(Rayleigh scattering?) 

Q101: A generalized dulling of the image by optical densities not representing 

diagnostic information. 

Image fog. 



Q102: The probability of _____ is inversely proportional to the third power of 

the x-ray energy. 

PE, (PE = K·Z 4 / E 3 ?) 

Q103: A PE interaction is more likely to occur with a _______ atomic number 

atoms. 

High. 




Increases proportionately with the cube of the atomic number (PE = K·Z 4 ?) 










Deep Scratches In Lead Screen For Radiography 

The number of electrons 

emitted per unit surface of the 

lead is essentially 

uniform. Therefore, more 

electrons can reach the film in 

the vicinity of a scratch, 

resulting in a dark line on the 

radiograph. (For illustrative 

clarity, electron paths have 

been shown as straight and 

parallel; actually, the electrons 

are emitted diffusely.) 


In considering the problem of demagnetiz 

ation, it is important to remember that a 

part may retain a strong residual field after 

having been circularly magnetized, and yet 

exhibit little or no external evidence of such a 

condition, as local poles are not easily 

detected. 圆形磁场极点不明显 

Such a field is difficult to remove, and there is no easy way to check the 

success of demagnetization. There may be local poles on a circularly 

magnetized piece at projecting irregularities or changes or sections, and 

these can be checked with a field indicator. However, to demagnetize a 

circularly magnetized part, it is often better to first convert the circular field to 

a longitudinal field. The longitudinal field does possess external poles, 

is more easily removed, and the extent of removal can be easily checked 

with a field indicator. 


http://chemical-biological.tpub.com/TM-1-1500-335-23/css/TM-1-1500-335-23_281.htm

Read More: 

https://www.nde-ed.org/TeachingResources/teachingresources.htm 



Good Luck!

Understanding NRT- Reading 1 of 2- Radiogaphic Testing A

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